U.S. patent number 6,296,463 [Application Number 09/141,959] was granted by the patent office on 2001-10-02 for segmented metering die for hot melt adhesives or other polymer melts.
This patent grant is currently assigned to Nordson Corporation. Invention is credited to Martin A. Allen.
United States Patent |
6,296,463 |
Allen |
October 2, 2001 |
**Please see images for:
( Certificate of Correction ) ** |
Segmented metering die for hot melt adhesives or other polymer
melts
Abstract
A segmented die assembly comprising a plurality of side-by-side
and separate units. Each die unit includes (a) a manifold segment
having an internal gear pump, (b) a die module mounted on the
manifold segment, and (c) a recirculating module mounted on the
manifold segment. The manifold segments are interconnected and
function to deliver process air and polymer melt to the modules.
Each die module includes (a) a fiberization nozzle, and (b) a valve
for controlling the flow of polymer therethrough. The gear pump of
each manifold segment receives a polymer melt and delivers it
either to the die module (with its valve open) or to the
recirculation module (with the die module valve closed). Polymer
melt flowing through the die module and is discharged as a filament
or filaments onto a moving substrate or collector. On the other
hand, polymer flow through the recirculation module is returned to
the polymer melt hopper or reservoir for recirculation through the
die assembly.
Inventors: |
Allen; Martin A. (Dawsonville,
GA) |
Assignee: |
Nordson Corporation (Westlake,
OH)
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Family
ID: |
26743645 |
Appl.
No.: |
09/141,959 |
Filed: |
August 28, 1998 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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063651 |
Apr 20, 1998 |
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Current U.S.
Class: |
425/7; 118/315;
156/500; 425/192S; 425/72.2 |
Current CPC
Class: |
B05B
7/0807 (20130101); B05C 5/027 (20130101); B05C
5/0279 (20130101); D01D 4/025 (20130101); D01D
5/0985 (20130101); B05C 11/1002 (20130101); B05C
5/0237 (20130101); B05C 11/1042 (20130101) |
Current International
Class: |
B05B
7/02 (20060101); B05B 7/08 (20060101); B05C
5/02 (20060101); B05C 11/10 (20060101); D01D
5/08 (20060101); D01D 4/02 (20060101); D01D
4/00 (20060101); D01D 5/098 (20060101); B29C
047/10 (); B29C 047/12 () |
Field of
Search: |
;425/7,72.2,81.1,83.1,186,192S ;118/315 ;156/167,500 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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68534594.6 |
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Dec 1985 |
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DE |
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0820817 |
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Jan 1988 |
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EP |
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WO 94/01221 |
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Jan 1994 |
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WO |
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Other References
Trends (1993) The CF 800 Metered Head..
|
Primary Examiner: Nguyen; Nam
Assistant Examiner: Leyson; Joseph
Attorney, Agent or Firm: Wood, Herron & Evans,
L.L.P.
Parent Case Text
RELATED APPLICATION
This application is a continuation-in-part of Application Ser. No.
09/063,651, filed Apr. 20, 1998 (now abandoned), the disclosure of
which is hereby fully incorporated by reference herein.
Claims
What is claimed is:
1. A segmented die assembly comprising:
(a) a plurality of manifold segments, each having an inlet polymer
flow passage and a polymer discharge flow passage formed therein;
said manifold segments being interconnected in side-by-side
relationship wherein said inlet polymer flow passages are in fluid
communication, respectively, and each manifold segment including a
rotary positive displacement pump for receiving a polymer melt from
said inlet polymer flow passage and discharging the polymer melt
into said polymer discharge flow passage, said positive
displacement pump including a driven rotary member;
(b) a shaft extending through said manifold segments and connected
to said driven rotary member of each manifold segment, said shaft
comprising a stub shaft mounted in each manifold segment, and said
stub shafts being interconnected in end-to-end relationship;
(c) a motor for driving said shaft so that said motor drives said
interconnected stub shafts as a unit whereby said rotary positive
displacement pump of each manifold segment pumps polymer melt into
its respective polymer discharge flow passage;
(d) a die module comprising (i) a die body mounted on each manifold
segment and having a polymer flow passage in fluid communication
with the polymer discharge flow passage of its associated manifold
segment; and (ii) a nozzle mounted on the die body and having a
polymer flow passage in fluid communication with said polymer flow
passage of its associated die body for receiving the polymer melt
and discharging a filament or filaments of the polymer melt
therefrom; and
(e) means for delivering a polymer melt to said inlet polymer flow
passage of each manifold segment whereby the melt is distributed to
said inlet polymer flow passages of the manifold segments and flows
in each segment to said pump, said discharge flow passage and said
flow passages of said die body and said nozzle.
2. The die assembly of claim 1, wherein at least two of said
manifold segments are identical.
3. The die assembly of claim 1, wherein the positive displacement
pump of each manifold segment comprises a gear pump.
4. The die assembly of claim 3, wherein each manifold segment
includes a recess and wherein said gear pump of each manifold
segment comprises a pair of intermeshed gears located internal to
said recess of said manifold segment, said recess sealed by an
adjacent manifold segment.
5. A segmented die assembly, comprising:
(a) a plurality of manifold segments interconnected in side-by-side
relationship, each manifold segment having
(i) an inlet polymer flow passage formed therein;
(ii) a rotary positive displacement pump mounted therein for
receiving a polymer melt from its respective inlet polymer flow
passage and discharging the polymer melt into a polymer discharge
flow passage, said positive displacement pump including a driven
rotary member; and
(iii) a stub shaft drivingly connected to said driven rotary
member;
(b) a means for interconnecting said stub shafts in end-to-end
relationship whereby rotation of said interconnected stub shafts
rotates said rotary member in unison;
(c) a motor for rotating said interconnected stub shafts whereby
said rotary positive displacement pump of each manifold segment
pumps polymer melt into its respective polymer discharge flow
passage;
(d) a die module comprising (i) a die body mounted on each manifold
segment and having a polymer flow passage in fluid communication
with said polymer discharge flow passage of its associated manifold
segment; and (ii) a nozzle mounted on said die body and having a
polymer flow passage in fluid communication with said polymer flow
passage of its associated die body for receiving the polymer melt
and discharging a filament or filaments of the polymer melt
therefrom; and
(e) means for delivering the polymer melt to said inlet polymer
flow passage of each manifold segment whereby the melt is
distributed to said inlet polymer flow passages of said manifold
segments and flows in each segment to the pump, said discharge flow
passage and said flow passage of said die body and said nozzle.
6. A die assembly manifold for operating a selectable number of die
modules and a corresponding number of recirculation modules, said
die assembly manifold comprising:
(a) a plurality of manifold segments corresponding to the
selectable number of die modules, said manifold segments being
interconnected in side-by-side relationship, each manifold segment
including:
(i) a polymer inlet flow passage in fluid communication with an
adjacent manifold segment forming a continuous polymer flow
passage;
(ii) a polymer discharge flow passage configured to provide a
pressurized polymer melt to the die modules and the recirculation
modules associated with the manifold segment;
(iii) a rotary positive displacement pump for receiving a polymer
melt from said polymer inlet flow passage and discharging the
pressurized polymer melt into said polymer discharge flow
passage;
(iv) a first die module instrument air passage for one of the
selectable number of die modules; and
(v) a first recirculation module instrument air passage for one of
the corresponding number of recirculation modules;
(b) a pair of end plates laterally closing the plurality of
manifold segments, said pair of end plates configured to provide
the polymer melt to said continuous polymer flow passage; and
(c) a pump drive shaft extending through said manifold segments and
connected to each rotary positive displacement pump to drive each
pump and maintain operating pressure of the polymer melt within
said manifold segments.
7. The die assembly manifold of claim 6, wherein the die modules
are pneumatically controllable by a die module pneumatic
controller, and each manifold segment further comprises:
a first input instrument air flow passage in gaseous communication
with the other manifold segments to form a continuous instrument
air input flow passage, said continuous instrument air input flow
passage configured to provide instrument air to the die module
pneumatic controller;
a first exhaust instrument air flow passage in gaseous
communication with the other manifold segments to form an exhaust
instrument air continuous flow passage, said exhaust instrument air
continuous flow passage configured to exhaust instrument air from
the die module pneumatic controller; and
a second die module instrument air passage, said first and second
die module instrument air passages each configured to be in gaseous
communication between the die module pneumatic controller and a
selected one of the die modules for selectively opening and closing
the selected one of the die modules.
8. The die assembly manifold of claim 7, wherein the recirculation
modules are pneumatically controllable by a recirculation module
pneumatic controller, each manifold segment further comprising:
a second input instrument air flow passage in gaseous communication
with the other manifold segments to form a second continuous
instrument air input flow passage, said second instrument air input
flow passage configured to provide instrument air to the
recirculation module pneumatic controller;
a second exhaust instrument air flow passage in gaseous
communication with the other manifold segments to form a second
exhaust instrument air continuous flow passage, said second exhaust
instrument air continuous flow passage configured to exhaust
instrument air from the recirculation module pneumatic controller;
and
a second recirculation module instrument air passage, said first
and second recirculation module instrument air passages each
configured to be in gaseous communication between the recirculation
module pneumatic controller and a selected one of the recirculation
modules for selectively opening and closing the recirculation
module.
9. The die assembly manifold of claim 6, wherein each die module
includes a meltblowing nozzle configured to discharge process air
to displace a filament dispensed by the die module, the pair of end
plates further configured to provide process air to said plurality
of manifold segments, each manifold segment further comprising:
a process air passage in gaseous communication with the other
manifold segments to form a continuous process air flow passage,
the process air flow passage configured to provide process air to a
respective one of the die modules.
10. The die assembly manifold of claim 9, wherein said process air
flow passage of each manifold segment comprises a plurality of
holes, said pair of end plates including slots coupling said
plurality of holes to form a continuous process air flow passage
adapted to be heated during multiple passes of the process air
through the plurality of manifold segments.
11. A die assembly for operating a selectable number of die modules
and a corresponding number of recirculation modules,
comprising:
(a) a plurality of manifold segments corresponding to the
selectable number of die modules, said manifold segments being
interconnected in side-by-side relationship, each manifold segment
including:
(i) a polymer inlet flow passage in fluid communication with an
adjacent manifold segment forming a continuous polymer flow
passage;
(ii) a polymer discharge flow passage configured to provide a
pressurized polymer melt to the die modules and the recirculation
modules associated with the manifold segment;
(iii) a rotary positive displacement pump for receiving a polymer
melt from said polymer inlet flow passage and discharging the
pressurized polymer melt into said polymer discharge flow
passage;
(iv) a first die module instrument air passage for one of the
selectable number of die modules; and
(v) a first recirculation module instrument air passage for one of
the corresponding number of recirculation modules;
(b) a pair of end plates laterally closing the plurality of
manifold segments, said pair of end plates configured to provide
the polymer melt to said continuous polymer flow passage;
(c) a pump drive shaft extending through said manifold segments and
connected to each rotary positive displacement pump to drive each
pump and maintain operating pressure of the polymer melt within
said manifold segments;
a motor operably coupled to said drive shaft to drive said
plurality of rotary positive displacement pumps; and
a plurality of die modules each comprising (i) a die body mounted
on one of said manifold segments and having an inlet polymer flow
passage in fluid communication with said polymer discharge flow
passage of its associated manifold segment; and (ii) a nozzle
mounted on said die body and having an inlet polymer flow passage
in fluid communication with said inlet polymer flow passage of its
associated die body for receiving the polymer melt and discharging
a filament or filaments of the polymer melt therefrom.
12. The die assembly of claim 11, wherein said nozzles of each die
module are arranged in a row, and each rotary positive displacement
pump of each manifold segment includes a driven rotating member
which rotates about an axis parallel to said row of nozzles.
13. The die assembly of claim 11, further including a recirculation
module mounted on each manifold segment and having an inlet polymer
flow passage in fluid communication with said polymer discharge
flow passage of its associated manifold segment.
14. The die assembly of claim 13, wherein the assembly further
includes a passage for recirculating the polymer melt from said
recirculation module to a means for delivering polymer melt to said
inlet polymer flow passage of each manifold segment.
15. A die assembly for operating a selectable number of die modules
and a corresponding number of recirculation modules respectively
configured for operation by a die module pneumatic controller and a
recirculation module pneumatic controller, the die assembly
comprising:
(a) a plurality of manifold segments corresponding to the
selectable number of die modules, said manifold segments being
interconnected in side-by-side relationship, each manifold segment
including:
(i) a polymer inlet flow passage in fluid communication with an
adjacent manifold segment forming a continuous polymer flow
passage;
(ii) a polymer discharge flow passage configured to provide a
pressurized polymer melt to the die modules and the recirculation
modules associated with the manifold segment;
(iii) a rotary positive displacement pump for receiving a polymer
melt from said polymer inlet flow passage and discharging the
pressurized polymer melt into said polymer discharge flow
passage;
(iv) a first die module instrument air passage for one of the
selectable number of die modules; and
(v) a first recirculation module instrument air passage for one of
the corresponding number of recirculation modules;
(b) a pair of end plates laterally closing the plurality of
manifold segments, said pair of end plates configured to provide
the polymer melt to said continuous polymer flow passage;
(c) a pump drive shaft extending through said manifold segments and
connected to each rotary positive displacement pump to drive each
pump and maintain operating pressure of the polymer melt within
said manifold segments;
(d) a first input instrument air flow passage in gaseous
communication with the other manifold segments to form a continuous
instrument air input flow passage, said continuous instrument air
input flow passage configured to provide instrument air to a die
module pneumatic controller;
(e) a first exhaust instrument air flow passage in gaseous
communication with the other manifold segments to form an exhaust
instrument air continuous flow passage, said exhaust instrument air
continuous flow passage configured to exhaust instrument air from
the die module pneumatic controller;
(f) a second die module instrument air passage, said first and
second die module instrument air passages each configured to be in
gaseous communication between the die module pneumatic controller
and a selected one of the die modules for selectively opening and
closing the selected one of the die modules;
(g) a second input instrument air flow passage in gaseous
communication with the other manifold segments to form a second
continuous instrument air input flow passage, said second
instrument air input flow passage configured to provide instrument
air to a continuous recirculation module pneumatic controller;
(h) a second exhaust instrument air flow passage in gaseous
communication with the other manifold segments to form a second
exhaust instrument air continuous flow passage, said second exhaust
instrument air continuous flow passage configured to exhaust
instrument air from the recirculation module pneumatic
controller;
(j) a second recirculation module instrument air passage, said
first and second recirculation module instrument air passages each
configured to be in gaseous communication between the recirculation
module pneumatic controller and a selected one recirculation module
for selectively opening and closing the recirculation module;
(k) a motor operably coupled to said shaft to drive said plurality
of rotary positive displacement pumps;
(l) a die module mounted on each manifold segment and having an
inlet polymer flow passage in fluid communication with said polymer
discharge flow passage of its associated manifold segment; and (ii)
a nozzle mounted on said die body and having an inlet polymer flow
passage in fluid communication with said inlet polymer flow passage
of its associated die body for receiving the polymer melt and
discharging a filament or filaments of the polymer melt therefrom;
and
(m) a recirculation module comprising a die body mounted on each
manifold segment, said die body having an inlet polymer flow
passage in fluid communication with said polymer discharge flow
passage of its associated manifold segment for receiving the
polymer melt and discharging a recirculated polymer melt.
16. The die assembly of claim 15, further comprising:
a die module pneumatic controller operably coupled to each manifold
segment for controlling the associated die module; and
a recirculation module pneumatic controller operably coupled to
each manifold segment for controlling the associated recirculation
module.
17. The die assembly of claim 16, wherein each pneumatic controller
comprises a solenoid valve.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to fiberization dies for applying
hot melt adhesives to a substrate or for producing nonwovens. In
one aspect the invention relates to a modular die provided with an
internal rotary positive displacement pump. In another aspect, the
invention relates to a segmented die assembly comprising a
plurality of separate die units, each unit including a manifold
segment and a die module and recirculation module mounted
thereon.
The deposition of hot melt adhesives onto substrates by
fiberization dies has been used in a variety of applications
including diapers, sanitary napkins, surgical drapes, and the like.
This technology has evolved from the application of linear beads
such as that disclosed in U.S. Pat. No. 4,687,137, to air-assisted
deposition such as that disclosed in U.S. Pat. No. 4,891,249, to
spiral deposition such as that disclosed in U.S. Pat. Nos.
4,949,668 and 4,983,109. More recently, meltblowing dies have been
adapted for the application of hot melt adhesives (see U.S. Pat.
No. 5,145,689). As the term suggests, "fiberization" refers to a
process wherein a thermoplastic melt is extruded into and set into
fibers.
Modular dies have been developed to provide the user with
flexibility in selecting the effective length of the fiberization
die. For short die lengths only a few modules need be mounted on a
manifold block. (See U.S. Pat. No. 5,618,566). Longer dies can be
achieved by adding more modules to the manifold. U.S. Pat. No.
5,728,219 teaches that the modules may be provided with different
types of die tips or nozzles to permit the selection of not only
the die length but the deposition pattern.
U.S. Pat. No. 5,236,641 discloses a metering die which comprises a
plurality of metering pumps which feed polymer to individual
regions of a single elongated die tip. The tip is mounted on a
single polymer manifold which has a plurality of side-by-side flow
channels which feed a predetermined number of orifices of the tip.
Each pump supplies polymer to a single channel. The pumps may be
turned on or off so that polymer flow may be discontinued to some
of the orifices of the integral elongate tip. In this design the
length of the die is not variable because the manifold and die tip
are of fixed length and are not formed from individual
segments.
At the present, the most commonly used adhesive fiberization dies
are intermittently operated air-assisted dies. These include
meltblowing dies, spiral nozzles, and spray nozzles.
Meltblowing is a process in which high velocity hot air (normally
referred to as "primary air" or "process air") is used to blow
molten fibers or filaments extruded from a die onto a collector to
form a nonwoven web or onto a substrate to form an adhesive
pattern, a coating, or composite. The terms "primary air" and
"process air" are used interchangeably herein. The process employs
a die provided with (a) a plurality of openings (e.g. orifices)
formed in the apex of a triangular shaped die tip and (b) flanking
air plates which define converging air passages. As extruded rows
of the polymer melt emerge from the openings as filaments, the
converging high velocity hot air from the air passages contacts the
filaments and by drag forces stretches and draws them down forming
microsized filaments. In some meltblowing dies, the openings are in
the form of slots. In either design, the die tips are adapted to
form a row of filaments which upon contact with the converging
sheets of hot air are carried to and deposited on a collector or a
substrate in a random pattern.
Meltblowing technology was originally developed for producing
nonwoven fabrics but recently has been utilized in the meltblowing
of adhesives onto substrates. Meltblown filaments may be continuous
or discontinuous.
Another type of die head is a spiral spray nozzle. Spiral spray
nozzles, such as those described in U.S. Pat. Nos. 4,949,668 and
5,102,484, operate on the principle of a thermoplastic adhesive
filament being extruded through a nozzle while a plurality of hot
air jets are angularly directed onto the extruded filament to
impart a circular or spiral motion thereto. The filaments thus form
an expanding swirling cone shape pattern while moving from the
extrusion nozzle to the substrate. As the substrate moves with
respect to the nozzle, a circular or spiral or helical bead is
continuously deposited on the substrate, each circular cycle being
displaced from the previous cycle by a small amount in the
direction of substrate movement. The meltblowing die tips offer
superior coverage whereas the spiral nozzles provide better edge
control.
Other fiberization dies include the older non-air-assisted bead
nozzles such as bead nozzles and coating nozzles.
SUMMARY OF THE INVENTION
The die assembly of the present invention may be viewed as a
fiberization device for processing a thermoplastic material into
fibers or filaments. (The terms "fibers" and "filaments" are used
interchangeably herein.) The fiberization may be air-assisted as in
meltblowing, spiral monofilaments, or melt spraying; or may be
non-air-assisted as in bead or coating depositions.
The fiberization of hot melt adhesives is the preferred use of the
die assembly of the present invention; but as will be recognized by
those skilled in the art, it can be used in the meltblowing of
polymers to form nonwoven webs.
The die assembly of the present invention features a number of
novel features, but in a broad embodiment, it comprises three main
components: a manifold segment; a fiberization die module; and a
recirculation module. The manifold, in a preferred embodiment,
includes an internal rotary positive displacement pump (e.g. gear
pump) for receiving a polymer melt from a polymer delivering system
(e.g. extruder) and discharging the same at a metered rate
(constant rate) to one of the modules. Each module includes a valve
for controlling the flow of the polymer melt therethrough. Controls
are provided so that the flow from the gear pump is uninterrupted;
that is, the pump discharge flows either to the fiberization die
module or the recirculation module. This is achieved by selectively
activating the valves of the fiberization die module and the
recirculating module. Generally, the flow will be to one or the
other module, but not both.
The preferred embodiment of the invention contemplates the use of a
plurality of the manifold segments (with each having the two
modules described above mounted thereon), interconnected in a
side-by-side relationship. The number of segment/module units
define the effective length of the die assembly. The side-by-side
fiberization die modules form a row of nozzles (e.g. meltblowing
die tips, spiral nozzles, etc.) for generating the fibers (or
filaments) and depositing the same onto a substrate or collector.
The driven rotary member of each internal gear pump rotates about
an axis generally parallel to the row of nozzles. In a preferred
embodiment, a motor driven shaft extends through the side-by-side
manifold segments along this axis of rotation and is keyed to each
driven rotary member. Thus, only one driven shaft is required for
the entire assembly.
An alternate embodiment of the present segmented die includes a
self-contained modular rotary pump in each segment, and wherein
each pump comprises metering gears and a segmented drive shaft. The
drive shaft of each pump has a tang at one end and a slot at the
opposite end. In the assembled configuration, the tang of one pump
shaft couples with the slot of the adjacent pump. The tang of the
adjacent pump will couple with the slot of the pump adjacent to it;
and so on along the die length. Thus in the modular pump
embodiment, the integral drive shaft whereon all the driven pump
gears are mounted is replaced with coupled drive shaft segments.
This embodiment has the advantage that die segments may be removed
or added without the need for disassembling the manifold, as well
as eliminating the need for using integral drive shafts of various
lengths to accommodate additional segments and pumps. The modular
pumps may also be preassembled and rapidly installed into the die
manifold.
In summary, the die assembly of the present invention comprises the
following novel features:
(a) a die with an internal metering pump;
(b) a die with a fiberization die module and a recirculation
module, and means for selecting the flow through each module;
(c) a plurality of manifold segments, each segment having an
internal metering pump;
(d) a plurality of side-by-side manifold segments having internal
metering pumps driven by a single shaft or a segmented shaft;
and
(e) a plurality of side-by-side manifold segments, each having a
fiberization die module and a recirculation module, and means for
selectively controlling the polymer melt flow to either module of
each manifold/module unit.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view of the present segmented die.
FIG. 2 is a top plan view, with portions cut away, of the die
illustrating die segments, gear pumps, and polymer flow
passages.
FIG. 3 is a top plan view illustrating the process and instrument
air flow passages.
FIG. 4 is a side semi-sectional view illustrating die modules,
recirculation modules, and gear pumps, with the cutting plane shown
generally by line 4--4 of FIG. 2.
FIG. 5 is a perspective view of a manifold segment, shown partially
exploded.
FIGS. 6 and 7 are side views of the interior surfaces of the die
endplates with the cutting planes taken generally along lines 6--6
and 7--7 of FIGS. 2 and 3, respectively.
FIG. 8 is a sectional view taken generally along line 8--8 of FIG.
4 illustrating the process air flow to the die modules.
FIG. 9 is an elevational view of the modular pump.
FIG. 10 is an exploded view showing the internal structure of the
modular pump.
FIG. 11 is an elevational view of an endplate and metering gears of
the modular pump.
FIG. 12 is a side view of a manifold segment for use with the
modular pump.
FIG. 13 is a top sectional view showing the coupling of the drive
shafts of the modular pumps.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As seen in FIG. 1, die assembly 10 comprises segmented manifold 11
(or die), fiberization die modules 12, recirculation modules 2, and
pneumatic controllers 3 and 4. Manifold 11 supplies a pressurized
molten polymer to module 12. Die module 12 has a die tip 13 through
which a molten polymer is extruded to form a stream of polymer
fibers or filaments 14 which are deposited on a moving collector or
substrate 9 to form a continuous or discontinuous layer 20.
Filaments 14 may be in the form of continuous or discontinuous
filaments as in meltblowing, or beads, sheets, or spirals as in the
application of adhesives.
As seen in FIGS. 2 and 3, manifold 11 is of segmented design
comprising a number of separate segments 11a-d interconnected in
side-by-side relationship and sealed at each end by endplates 7 and
8.
Since the segments 11a-11d are substantially identical in
structure, reference numerals without lower case letters will
represent corresponding parts in each segment. In describing the
assembly, reference numerals with lower case letters (e.g. 11a-11d)
will represent the corresponding parts of the assembly.
General Description
Each segment 11a-11d contains rotary positive displacement pump
15a-15d and associated flow passages which feed molten polymer to
die modules 12a-d in parallel and are discharged therefrom as
filaments 14. The manifold segments 11a-d also contain flow
passages which feed polymer from pumps 15a-d to recirculation
modules 2a-d. Pneumatic controls 3a-d and 4a-d activate valves
within modules 12a-d and 2a-d which can be selectively and
individually opened or closed to control the flow of polymer to
either module. In the operational mode, the controls of an
individual segment will activate the valves which route the flow of
polymer to the die module 12 and there will be flow to the
recirculation module 2. In the by-pass or recirculation mode the
controls route the polymer to the recirculation module 2 where the
polymer is recirculated to a polymer supply reservoir (not shown)
and no polymer is discharged from the die module 12. By controlling
which of segments 11a-d are in the operational mode or in the
recirculation mode, different patterns of polymer may be discharged
from the die modules.
Rotary pumps 15a-d act as metering pumps which when in the
operational mode will deliver polymer to each die module 12 at
substantially the same rate. The variation in polymer flow rate
from module to module will typically be less than 5% thus providing
excellent uniformity along the die length. The rotary pumps 15a-15d
are preferably gear pumps that provide a constant output for a
given rpm.
One feature of the segmented design is that segments may be added
or removed to vary the die length from application to
application.
As described below, in a preferred embodiment, the fiberization
module 12 is provided with an air-assisted nozzle (e.g.
meltblowing, spray, or spiral). End plate 7 has process air inlet
29 which feeds air passages formed in manifold 11. The air flows
through manifold 11 and is delivered to the die modules 12a-d in a
parallel flow pattern. The process air assists in the formation of
filaments 14 as will be described.
Each of the main components and functions of the segmented manifold
with internal metering pumps, die module, recirculation module, and
controllers of the die assembly 10 are described in detail
below.
Die Modules
The preferred die modules 12 for fiberizing the polymer melt are
the type described in U.S. Pat. Nos. 5,618,566 and 5,728,219, the
disclosures of which are incorporated herein by reference. It
should be understood, however, that other die modules may be used.
See, for example, U.S. patent application Ser. No. 09/021,426,
filed Feb. 10, 1998, entitled "MODULAR DIE WITH QUICK CHANGE DIE
TIP OR NOZZLE," now U.S. Pat. No. 6,210,141.
As best seen in FIG. 4, each die module 12 consists of a die body
16 and a die tip 13. The die body 16 has formed therein an upper
circular recess 17 and a lower circular recess 18 which are
interconnected by a body opening 19. The upper recess 17 defines a
cylindrical chamber 23 which is closed at its top by threaded plug
24. A valve assembly 21 mounted within chamber 23 comprises piston
22 having depending therefrom stem 25. The piston 22 is
reciprocally movable within chamber 23, with adjustment pin 24a
limiting the upward movement Conventional o-rings may be used at
the interface of the various surfaces for fluid seals as
illustrated.
Side ports 26 and 27 are formed in the wall of the die body 16 to
provide communication to chamber 23 above and below piston 22,
respectively. As described in more detail below, the ports 26 and
27 serve to conduct air (referred to as instrument gas) to and from
each side of piston 22.
Mounted in the lower recess 18 is a threaded valve insert member 30
having a central opening 31 extending axially therethrough and
terminating in valve port 32 at its lower extremity. The lower
portion of insert member 30 is of reduced diameter and in
combination with the die body inner wall defined a downwardly
facing cavity 34. Upper portion 36 of insert member 30 abuts the
top surface of recess 18 and has a plurality (e.g. 4) of
circumferential ports 37 formed therein and in fluid communication
with the central passage 31. An annular recess 37a extends around
the upper portion of 36 interconnecting the ports 37.
Valve stem 25 extends through body opening 19 and axial opening 31
of insert member 30, and terminates at end 40 which is adapted to
seat on valve port 32. The annular space 45 between stem 25 and
opening 31 is sufficient for polymer melt to flow therethrough.
Stem end 40 of stem 25 seats on port 32 with piston 22 in its lower
position within chamber 23. As discussed below, actuation of the
valve stem 25 moves end 40 away from port 32 (open position as
illustrated in FIG. 4), permitting the flow of polymer melt
therethrough. Melt flows from the manifold segment 11a through side
port 38, through 37, through the annular space 45 around stem 25
discharging through port 32 into the die tip assembly 13.
Conventional o-rings may be used as the interface of the various
surfaces as illustrated in the drawings.
The die tip assembly 13 illustrated in the drawings comprises a
stack up of four parts: a transfer plate 41, a die tip 42, and two
air plates 43a and 43b. The assembly 13 can be preassembled and
adjusted prior to mounting onto the die body 16 using bolts 50.
Transfer plate 41 is a thin metal member having a central polymer
opening 44 formed therein. Two rows of air holes 49 flank the
opening 44 as illustrated in FIG. 4. When mounted on the lower
mounting surface of body 16, the transfer plate 41 covers the
cavity 34 and therewith defines an air chamber with the air holes
49 providing outlets for air from cavity 34 on each side of opening
44. Opening 44 registers with port 32 with an o-ring providing a
fluid seal at the interface surrounding port 32.
The die tip 42 comprises a base member which is co-extensive with
the transfer plate 41 and the mounting surface of die body 16, and
a triangular nose piece 52 which may be integrally formed with the
base.
As described in U.S. Pat. No. 5,618,566, the nose piece 52
terminates in apex which has a row of orifices spaced therealong
and air plates 43a, 43b are in flanking relationship to the nose
piece 52 and define converging air slits 67a, 67b which discharge
at the apex of nose piece 52. Process air is directed onto opposite
sides of the nose piece 52 into the converging air slits 67a, 67b
and discharge therefrom as converging air sheets which meet at the
apex of nose piece 52 in space 56 and contact filaments 14 emerging
from the row of orifices 53. Process air is delivered from manifold
segment 11a to the die body 16 through port 39.
Also useable in the present invention are modules 12 disclosed in
U.S. Pat. No. 5,728,219 and U.S. patent application Ser. No.
09/021,426, filed on Feb. 10, 1998, now U.S. Pat. No. 6,210,141.
Other types of modules 12 may also be used. The modules 12 may
dispense meltblowing, spirals, beads, sprays or polymer coatings
from the nozzle. Thus the module 12 may be provided with a variety
of nozzles including meltblowing nozzles, spiral spray nozzles,
bead nozzles, and coating nozzles.
Recirculation Module
As best seen in FIG. 4, recirculation module 2 comprises upper body
54 which is of the same design as body 16 of die module 12. Module
2 comprises valve assembly 55 which operates in the same manner as
valve assembly 21 of module 12. Assembly 55 comprises pistion 57
and valve stem 58 which, when pneumatically activated by controller
5, will open 22, stem 25, and port 32 of die module 12.
With valve assembly 55 open, a molten polymer will enter module 2
from manifold passage 78 through port 61, flow around stem 58 and
through port 59 into lower recirculation block 62. Block 62, for
convenience of manufacture, may be constructed in one piece, or as
illustrated in two pieces. The block 62 may be mounted on the body
54 by bolts (not shown), or by a quick change connector described
in U.S. patent application Ser. No. 08/820,559, filed Mar. 19,
1997, now abandoned. Block 62 has orifice 63 which registers with
port 59 and polymer flow passage 64. Orifice 63 intersects flow
passage 66 which leads to right-angled passage 67 and module outlet
69. Outlet 69 registers with manifold segment inlet 71 which
discharges the polymer to passage 72 which recirculates the polymer
back to a supply tank (not shown). In the recirculation mode, valve
21 of the associated die module 12 will be closed and valve 55
opened. Passage 66 extends to outer outlet 65 which is sealed by
plug 65a.
Manifold Construction
Segmented manifold 11 comprising segments 11a-d and end plates 7
and 8 are secured together using a plurality of countersunk bolts
arranged in an alternating pattern. Referring to FIG. 2, each
manifold segment 11a-11d has a plurality of bolt hole pairs with
one hole being a threaded hole and the other hole being a bored and
countersunk hole.
Segment 11a, for example, contains hole 91a which is threaded and
hole 92a which is bored and countersunk as at 97a. Segment 11b
likewise has threaded hole 91b and bored and countersunk hole 92b.
For joining segments 11a and 11b, bolt 93a passes through bored
hole 92a and is threaded into hole 91b and tightening of bolt 93a
joins segments 11a and 11b. Segment 11c is likewise joined to
segment 11b using bolt 93b which passes through bored and
countersunk hole 92b into threaded hole 91c. The pattern is
repeated over the length of the segments 11a-11d at several
locations 91d-91h (threaded holes) and 92c-92h (bored and
countersunk holes). The bolt hole pattern alternates between
adjacent segments so that a bored and countersunk hole will always
align with a threaded hole. In other words, in adjacent segments
11, the locations of holes 91a-91h and 92a-92b will alternate. End
plate 7 is joined to segment 11a and end plate 8 is joined to
segment 11d in a similar manner as illustrated in FIG. 2 at 97 and
98, respectively.
Upon tightening bolts 93a-93h (at all locations 92a-92h) a
metal-on-metal fluid seal between segments 11a and 11b is
established around registering polymer and air flow passages.
Similarly, tightening bolt 93b creates a fluid seal between
segments 11b and 11c. The depth of the 15 countersunk hole 92a-92h
in each location is sufficient so that the head of the bolt 93a-93h
therein lies below the opening of the hole 92a-92h and, therefore,
when the bolts 93a-93h are tightened the lateral surfaces of the
segments 11a-11d and end plates 7, 8 are flush with one
another.
A large o-ring 89 in a suitable groove 89a (shown in FIG. 5) is
provided around pump housing 73 as seen in FIG. 4 to seal the
pump.
Referring to FIGS. 2, 3, 4 and 5 manifold 11 is of segmented design
and comprises segments 11a-d. Although four segments 11a-11d are
shown this is by way of illustration only and the number of
segments may vary over a wide range depending on the application.
Manifold 11 also comprises end plates 7 and 8. Plate 8 has a
polymer inlet 81 which feeds all of the segments 11a-11d through
continuous flow passage 75. Each segment 11a-11d also has a
machined recess 73a-d which houses a rotary positive displacement
pump (e.g. gear pumps 15a-d), respectively, and registers with
polymer inlet passage 75. Each pump 15a-15d comprises a pair of
intermeshing gears 82a-d and 83a-d. Keyed gears 82a-d (driven
members) are driven simultaneously by a motor 84 connected to the
gears by a continuous shaft 85 through a coupling 86, forming a
drive system 87. As viewed in FIG. 4, gears 82a-82d are driven in a
clockwise direction causing gears 83a-83d to rotate in the
counterclockwise direction. Gears 83a-d are supported on continuous
free-wheeling shaft 80.
Gears 82a-d and 83a-d have slip fits on shafts 85 and 80,
respectively. Shaft 85 is sealed using an o-ring (not shown)
disposed around the shaft 85 in end plate 8.
Although not shown, the drive system 87 may also include electric
controls to vary the speed of the motor 84 and a gearbox speed
reducer to reduce the speed of the pump drive shaft 85 from that of
the motor shaft. For illustration purposes only, the motor speed
may be in the range of 1500 to 2000 rpm whereas the speed of shaft
85 may be in the range of 0 to 105 rpm so that a 20:1 speed reducer
may be required. Motor speed control and shaft speed reduction are
within the realm of well-known art in the field and may vary within
broad ranges to fit almost any application.
Polymer entering through inlet 75 is entrained between the teeth of
each gear 82a-82d, 83a-83d as at 88 and carried thereby in the
rotating direction into lower part of housing 73 and into central
passage 76 which registers with the bottom (downstream side) of
housing 73. The clearance between the gears 83a-83d and the walls
of each housing 73a-73d is very small so that polymer between the
gear teeth 88 cannot escape and, therefore, the pumps 15a-15d
function as positive displacement pumps wherein the throughput of
polymer through each pump 15a-15d is determined by the speed at
which the gears 82a-82d, 83a-83d are driven. Gear pumps 15a-d are
of substantially the same design as those disclosed in U.S. Pat.
No. 5,236,641 the disclosure of which is incorporated herein by
reference.
As shown in FIG. 4, pump 15 delivers a pressurized molten polymer
to the central passage 76, then to a discharge flow passage 77 to
the fiberization die module 12 and to a manifold passage 78 leading
to the recirculation module 2. In the assembled segments 11a-d, as
best seen in FIGS. 2 and 4, pumps 15a-d deliver pressurized molten
polymer to the fiberization die or the recirculation module.
Passages 76a-d are individual passages within each segment and do
not communicate with passages of adjacent segments. Passages 76a-d
register with passages 77a-d which feed die modules 12a-d through
ports 38a-d in the operating mode, respectively. On the opposite
side passages 76a-d register with passages 78a-d which feed modules
2a-d through ports 61a-d in the recirculation mode. Because of the
complexity of the structure, FIG. 4 illustrates one side of
manifold segment 11c and sections of the modules 12 and 2 mounted
thereon from a perspective of irregular line 4--4 of FIG. 2. It is
recognized that several of the flow passages 77, 78, 71, 114, 116,
117, 123 should be properly represented by dashes--because they are
hidden--but for clarity of description these passages are shown in
solid lines.
Gear pumps 15a-d rotate at the same speed and deliver a pressurized
polymer to polymer discharge passages 76a-d. The polymer therein
will either flow to an individual die module 12 or to the
associated recirculation module 2. By way of illustration, consider
the case where it is desired to deliver polymer to die modules
11a-c only. In this instance valves 21a-c of the die modules
12a-12c would be opened by controllers 3a-c and valves 55a-c would
be closed by controllers 4a-c, whereas die module valve 21d would
be closed and valve 55d opened respectively by controllers 3d and
4d. Polymer would thus flow in parallel from passages 76a-c through
passages 77a-c into modules 12a-c and be extruded to form polymer
streams 14a-c on one side of the manifold 11. On the other side of
the module 11, passage 76d will deliver polymer to passage 78d and
recirculation module 2d. As has been described, the polymer will
flow through module 2d and be recirculated via passage 72 within
manifold 11 to the polymer supply reservoir. Any other
operation/recirculation combination of segments 11a-d is also
possible by selectively programming controller 3a-d and 4a-d.
Outlet 72a-72d of each segment 11a-11d is aligned with the
corresponding outlets 72a-72d of the other manifold segments
11a-11d and thus serves as a common outlet for all of the
recirculation modules. Each individual module outlet 69a-d
registers with an individual manifold inlet 71a-d (shown as 71 in
FIG. 4), which all register with a continuous outlet flow passage
72 extending the length of the manifold 11 which has an outlet 72a
at one side of the die which leads to a supply tank.
As has been mentioned, pumps 15a-d are rotary positive displacement
pumps whose throughput is determined by the speed of the pump. In
this way the pumps act as flow meters for delivering the polymer at
a very precise flow rate. Furthermore, because all the pumps
operate at the same speed the flow rate of polymer to each die
module will be the same (typically less than 5% variation from
module-to-module). The result is an extremely uniform polymer
stream 14 and end-product 20 (see FIG. 1) over the die length.
An important aspect of the present design is that the polymer flow
system downstream of pumps 15a-d while in the operational mode
(i.e. flow through die modules 12a-12d) is constantly under
pressure induced by the pumps. When switching a segment from
operational mode to recirculation mode it is important to maintain
the same operating pressure so that there will be a smooth
transition in polymer flow when the segment is switched back to the
operational mode. If the pressure is significantly higher or lower
than the operating pressure while in the recirculation mode, a
transient such as a surge in polymer flow through the die module
may occur when the segment is switched again from the recirculation
to the operational mode.
Maintaining operating pressure while in the recirculation mode is
accomplished by sizing orifice 63 in the recirculation block 62 in
relation to the viscosity of the polymer being processed so that
the orifice 63 will provide the correct amount of flow resistance
to maintain operating pressure upstream of the orifice 63.
Different size orifices 63 are required for different polymers.
In another preferred embodiment, outlet 72a may be sealed with a
threaded plug (not shown), and plug 65a at outlet 65 may be
removed. A spring-loaded needle valve (not shown) may be disposed
in outlet 65 wherein the tension in a spring determines the
pressure required to displace a needle of the valve and thereby
regulate the operating pressure. A recirculation hose (not shown)
may be connected to the outlet 65 and to the polymer supply tank.
An adjustable needle valve may be provided to allow variation of
operating and recirculation pressure through valve spring tension
for polymers having different flow properties.
Another important aspect of the present invention is the location
of the rotary positive displacement pumps 15a-15d internal to each
manifold segment 11a-11d. This streamlines the structure and
facilitates connecting a single drive shaft 85 to all the pumps
15a-15d in the manifold 11. The axis of rotation of the driven
gears 82a-82d is parallel to the row of fiber forming means of the
assembled manifold 11.
Electric heaters 70 may be provided in the aligned segments 11a-11d
to maintain the polymer melt flowing through the manifold segments
11a-11d at the proper temperature.
Modular Pump
In an alternate preferred embodiment of the present metering die,
each pump 15a-15d which is assembled within manifold 11 is replaced
with a self-contained modular pump 130, depicted in FIGS. 9-13.
Manifold segment 11 is modified to contain a cavity wherein the
modular pump is placed for operation. The modular pumps are of
rotary gear design and similar to non-modular pumps 15a-din terms
of the principles of operation (i.e. polymer flow and
metering).
Returning to the first embodiment as seen in FIG. 2, driven gears
82a-d are mounted on integral drive shaft 85 which extends through
each manifold segment 11a-11d, and gears 83a-d are supported on
integral shaft 80. The lengths of shafts 85 and 80 must be sized in
relation to the number of manifold segments 11a-11d to be used.
Adding or removing manifold segments 11a-11d would require
replacing the two shafts 85, 80 with shafts 85, 80 of different
lengths. Therefore, to add even a single segment onto the end of
the die, all the gears 82a-82d, 83a-83d on the two shafts 85, 80
would have to be removed and remounted on new shafts 85, 80 in the
configuration described previously in relation to FIGS. 2, 4, and
5. The only way this can be accomplished is to disconnect each
manifold segment 11a-11d, which amounts to disassembling the entire
manifold 11. Note also that if a pump 15a-15d becomes clogged or
damaged requiring cleaning or replacement, a similar situation
arises. Disassembling the manifold is time-consuming and
inefficient. In addition, housing 73 (including o-ring groove 89a)
in manifold 11 is expensive to manufacture.
The modular pump described below is designed to overcome these
difficulties. A principal advantage of the modular pump 130a-130d
is that each pump 130a-130d comprises its own drive shaft 143 that
connects to the drive shafts 143 of adjacent pumps 130a-130d using
a tang-in-slot coupling. Each pump 130a-130d also has its own idler
shaft 149 as will be described. Thus, integral shafts 85 and 80 are
replaced with segmented shafts. The modular design allows manifold
segments to be added or removed without the need to disassemble the
entire manifold. Housing 73 in the manifold segment 11 is replaced
with a simplified mounting cavity for the modular pump that is less
expensive to manufacture.
With reference to FIGS. 9 and 10, modular pump 130 comprises
endplates 131 and 132 and center plate 133 sandwiched therebetween.
Note in FIG. 13 four pump units are shown labeled 130a-10d.
Endplate 131 has pins 136 and 137 which mate with holes in plates
132 and 133 for precisely aligning the plates. Plate 132 has
countersunk and bored holes 137a-e whereas middle plate 133 has
clearance holes 138a-e and endplate 131 has threaded holes 139a-e.
Bolts (not shown) are inserted into holes 137a-e, pass thorugh
holes 138a-e and are threaded into holes 139a-e for joining the
three plates together and for providing a fluid seal at the
interfaces of the plates. Holes 137a-e are sized so that the heads
of the bolts do not extend beyond the outer surface of plate
132.
As seen in FIGS. 10 and 11, pump 130 also comprises intermeshing
gears 141 and 142 rotatably disposed in housing 140 formed in
center plate 133. Gear 141 is a driven gear and 142 is an idler
gear. The thickness of plate 133 is slightly larger than that of
gears 141 and 142 so that the gears 141, 142 are free to rotate
after plates 131, 132 and 133 have been bolted together. Pump 130
further comprises drive shaft 143 having tang 144 at one end and
slot 145 on the opposite end. Shaft 143 passes through holes 146
and 147 in the endplates 131 and 132, respectively. The holes are
slightly larger than the diameter of the shaft so that the shaft is
free to rotate. The holes are sized, however, so that they provide
a bearing-type support for the drive shaft as it rotates. Driven
gear 141 is secured to shaft 143 using a key inserted in slot 148
and a corresponding slot in the shaft (not shown).
As best seen in FIG. 10, idler shaft 149 is press fit into hole 151
of plate 131 at one end, passes rotatably through the center hole
of idler gear 142, and is press fit into hole 152 of plate 132. The
press fit into holes 151 and 152 is accomplished as the plates are
bolted together. The press fit on each end of shaft 149 establishes
a fluid seal between the shaft and the endplates.
Manifold segment 150 (FIG. 12) has formed therein pump cavity 153.
The outer dimensions of the cavity are slightly larger by about
0.01 inch than the outer periphery of the modular pump so that the
pump fits into the cavity without requiring a press fit. The width
of pump 130 is approximately 0.001 inches smaller than the depth of
cavity 153. Pump 130 is manufactured from a type of steel that has
a higher thermal expansion rate than the steel used for manifold
150. The pump width is smaller than the cavity depth to allow for
the pump to expand as the die is heated. The preferred overall
thickness of pump 130 is between 0.5 and 0.7 inches.
Manifold 150 has polymer outlet 155 which registers with polymer
inlet 154 of pump 130 (see FIGS. 9 and 10) with the pump 130
inserted into the cavity 153. The outlet of the pump 130 is formed
in endplate 131 as best seen in FIGS. 10 and 11. The outlet
comprises recess 160 which opens into flow channels 156 and 157.
Channel 156 has outlet hole 158 which registers with inlet 159 of
manifold 150 for feeding die module 12. Channel 157 has outlet 161
which registers with manifold inlet 162 for feeding recirculation
module 2. Thus polymer enters the pump at inlet 154, is entrained
by the teeth of gears 141 and 142, flows around the outer periphery
of the gears (gear 141 is driven clockwise as viewed in FIG. 11)
into recess 160, into channels 156 and 157, into outlets 158 and
161, and enters the manifold at 159 and 162. After the polymer
leaves pump 130 to either the die module or the recirculation
module, the polymer flow is the same as has been described with
reference to non-modular pump 15. The process air flow and
instrument gas flow (described below) are identical to the
embodiment of FIGS. 3 and 4.
Pump 130 also comprises outlet hole 163 which allows polymer to
flow into an adjacent manifold and pump segment. Thus a portion of
the polymer entering the pump flows through the pump and the rest
flows through hole 163 into a neighboring segment. With a plurality
of manifold segments 11 and pumps 130 assembled in stacked
relation, holes 154, 155, and 163 of all the segments form a
continuous flow passage along the length of the die. o-rings (not
shown) are provided around polymer holes 155, 159, 162, and shaft
hole 164 in manifold 150 to establish fluid seals between the
manifold and pump 130. O-rings are also provided around the outside
of hole 163 and shaft hole 147 of pump plate 132 to establish a
seal at the abutting surface of the adjacent manifold segment.
The present modular pump 130a-130d wherein each pump 130a-130d has
its own drive shaft 143 and idler shaft 149 allows segments 11 to
be added or removed without the necessity of disassembling the
manifold. As seen in FIGS. 12 and 13, manifold 150 has hole 164
which allows pump drive shaft 143 to pass therethrough. Shaft 143
has tang 144 at one end and slot 145 at the other end. As best seen
in FIG. 13, adjacent pumps are oriented so that the slot of one
shaft will align and mate with the tang of the adjacent shaft as
shown at 144a and 145b, 144b and 145c, and so on along the length
of the die. Drive shaft 165 has slot 168 which is coupled to tang
144d of pump shaft 143d. Drive shaft 165 passes through endplate
166 and is coupled to a motor (not shown) for driving all of the
coupled shafts 143a-d together. Cavity 153 of manifold 150 is
slightly oversized (viz. 0.01 inch) in relation to the outer
dimensions of pump 130 so that in the coupled configuration each
pump 130 may move slightly whereby no binding between the coupled
shafts 143a-143d occurs. Also a small amount of tolerance between
the tang 144 and slot 145 is provided to eliminate binding.
The present design allows segments to be added or removed without
the need for replacing the drive shaft 85 and idler shaft 80 as in
the integral shaft design of FIG. 2. For example if segment 150a in
FIG. 13 is to be removed, die endplate 167 will be unbolted from
segment 150a, the segment along with pump 130a will be unbolted and
disconnected from segment 150b with drive shafts thereof being
uncoupled at 144a and 145b, and endplate 167 bolted onto segment
150b to complete the procedure. Manifold segments 150a-d are bolted
together in the same fashion as has been described in relation to
FIG. 2. The polymer flow through from the manifold to the inlets of
modules 12 and 2 is the same as has been described in relation to
FIGS. 2 and 4.
Process Air Flow
Referring to FIGS. 2 through 7, heated process air enters through
inlet 29 which registers with circular groove 101 (FIG. 6) formed
along the inner wall of the endplate 7. Middle segments 11a-d have
a plurality of holes 102a-h which when assembled form continuous
flow passages 103a-h which travel the length of the die 11 as seen
in FIG. 3 (103c,d not shown). Process air inlet 29 registers with
groove 101 as seen in FIG. 6. The inlets of passages 103a-d
register with groove 101 so that air entering the groove via inlet
29 will enter the passages and flow the length of the die from
plate 7 to plate 8 in parallel. The outlet of passages 103a-d
register with groove 106 formed in end plate 8 (FIG. 7). Groove 106
also registers with inlets to flow passages 103e,f which turns the
air and causes the air to flow back along the length of the die in
the direction opposite that of passages 103a-d. The outlets to
passages 103e,f register with groove 107 formed in plate 7 which
receives the air and turns the air again to travel back along the
length of the die through passage 103g which discharges into groove
108 of end plate 8. A portion of the air travels back along the die
length through passage 103h while the rest of the air flows from
groove 108 towards the manifold discharge through slot 109 in plate
8. Air which returns to plate 7 through passage 103h flows towards
the manifold discharge through slot 111. Thus the air makes three
or four passes along the length of the die before being discharged
to the die modules. The direction of air flow in passages 103a-h is
illustrated by arrows 90 in FIG. 3. Central heating element 112
heats the multi-pass air to the operating temperature. Because the
process air temperature is hotter than the polymer operating
temperature isolation slots 99 are provided in plates 7 and 8, and
11a-d to disrupt heat flow between the process air flow and polymer
flow passages of the manifold.
As seen in FIGS. 3 and 8, process air flows towards the manifold
discharge along both sides of the manifold through slots 109 and
111. Plates 11a-f have holes which define air passage 113 which
extends the length of the die. Slots 109 and 111 discharge from
opposite sides into passage 113 which feeds in parallel holes
114a-d which in turn feed air inputs 39a-d in die modules 12a-d,
respectively. The air flows through the die modules as has been
described and is discharged as converging sheets of air onto fibers
14 extruded at die tip apex 56.
Instrument Air
Referring to FIGS. 2 and 3 each die module 12 and recirculation
module 2 have valve assemblies which are activated (opened or
closed) by a pneumatic controller (actuator) 3 and 4, respectively.
The operation of each controller is identical and, therefore, only
actuator 3 for the die module will be described it being understood
that the functioning of recirculation actuator 4 will be the same.
The same reference numerals for the instrument air passages and
controls for actuating the valve assembly 55 of recirculation
module 2 are used for corresponding passages and controls for
activating die module 12. It is also to be understood, however,
that associated actuators (e.g. 3a and 4a) will generally operate
in opposite modes. When controller 3a commands die module valve 21a
to open, controller 4a will simultaneously command recirculation
module valve 55 to be closed and visa-versa. However, as has been
described some die segments may be in the operational mode (polymer
flow to die modules) while others are in the recirculation mode
(polymer flow to recirculation module) to produce stream 14 having
different patterns.
Each die module comprises a valve assembly 21 which is actuated by
compressed air acting above or below piston 22. Instrument air is
supplied to the top and bottom air chambers on each side of valve
piston 22 (see FIG. 4) by flow lines 116 and 117 formed in each
middle plate 11a-d. Controller 3 comprises three way solenoid valve
120 with electronic controls 121 to control the flow of instrument
air. Instrument air enters the die through inlet 115 into
continuous flow passage 118 which serves all the die segments (the
configuration of inlet 115 and passage 118 in relation to the
modules is illustrated in FIG. 3 for the recirculation modules, the
configuration being the same for the die modules). Passage 119 in
each segment delivers the air in parallel (see FIG. 3) to each of
solenoid valves 120a-d (shown schematically in FIG. 4). The valve
delivers the air to either passage 116 or 117 depending on whether
the module valve 21 is to be opened or closed. As illustrated in
FIG. 4, pressurized instrument air is delivered via line 117 to the
bottom of the piston 22 which acts to force the piston upward,
while the controller simultaneously opens the air chamber above the
piston (to relieve the air pressure above) to exhaust port 122 via
lines 116 and 123. In the upward position, valve stem 25 unseats
from port 32 thereby opening the polymer flow passage to the die
tip. In the closed position, solenoid 120 would deliver pressurized
air to the upper side of piston 22 through line 116 and would
simultaneously open the lower side of the piston to exhaust port
124 via line 125. The pressure above the piston forces the piston
downward and seats valve stem 25 onto port 32 thereby closing the
valve. Thus in a preferred mode each die module has a separate
solenoid valve such that the polymer flow can be controlled through
each die module independently. In this mode side holes 126 and 127
which intersect passages 116 and 117, respectively, are
plugged.
In a second preferred embodiment a single solenoid valve may be
used to activate valves 21 in a plurality of adjacent die modules.
In this configuration the tops of holes 116 and 117 (labeled 116a
and 117a) are plugged and side holes 126 and 127 opened. Side holes
126 and 127 are continuous holes and will intersect each of the
flow lines 116 and 117 to be controlled. Thus in the closed
position, pressurized air would be delivered to all of the die
modules simultaneously through hole 126 while hole 127 would be
opened to the exhaust. The instrument air flow is reversed to open
the valve.
As has been stated the principle of operation of the controllers 4
is the same as has been described for controls 3. The mode of
operation (i.e. operational mode/recirculation mode), however, of
controller 4 will generally be opposite that of controller 3.
Manifold segments 11a-d and endplates have inwardly tapered
surfaces 128 beneath controllers 3a-d and 4a-d to provide a large
heat transfer surface area. This is done to dissipate sufficient
heat to maintain the area above the tapers at a low temperature to
protect the electronic controls of controllers 3 and 4.
Assembly and Operation
As indicated above, the modular die assembly 10 of the present
invention can be tailored to meet the needs of a particular
operation. As illustrated in FIGS. 1, 2 and 3, four die segments
11a-d, each about 0.75 inches in width are used in the assembly 10.
The manifold segments 11 are bolted together as described
previously, and the heater elements installed. The length of the
heater elements will be selected based on the number of segments 11
employed and will extend through most segments. The die modules 12
and recirculation modules 2 may be mounted on each manifold segment
11 before or after interconnecting the segments 11, and may include
any of the nozzles 13 previously described. These may include
meltblowing nozzles (die tips), spiral spray nozzles, bead or
coating nozzles, or combinations of these.
A particularly advantageous feature of the present invention is
that it permits (a) the construction of a meltblowing die with a
wide range of possible lengths, interchangeable manifold segments,
and self contained modules, (b) variation of die nozzles (e.g.
meltblowing, spiral, or bead applicators) to achieve a
predetermined and varied pattern, (c) metering of polymer flow rate
to each nozzle to provide uniformity along the die length, and (d)
the production of polymer coatings having a pre-determined pattern.
The segments 11 are assembled by installing each segment on the
shaft, bolting the segment in place, and continuing the addition of
segments until the desired number has been installed on the
shaft.
Variable die length and adhesive patterns may be important for
applying adhesives to substrates of different sizes from one
application to another. The following sizes and numbers are
illustrative of the versatility of the modular die construction of
the present invention.
Die Assembly Broad Range Preferred Range Best Mode Number of
Segments 1-1,000 2-100 5-50 Length of each Segment 0.25-1.50"
0.5-1.00" 0.5-0.8" in machine direction (inches) Different Types
2-4 2-3 2 of Nozzles (13) (e.g. meltblowing, spiral, spray, and
bead)
The lines, instruments, and controls are connected and operation
commenced. A hot melt adhesive is delivered to the die 10 through
line 81, process air is delivered to the die through line 29, and
instrument air or gas is delivered through line 115.
Although the preferred embodiment of the present invention is in
connection with a plurality of manifold/module segments, there are
aspects of the invention applicable to single manifold/module
constructions or unitary dies. For example the internal metering
pump can be used with advantage on most any type of fiberization
die. Also, the recirculation module can be used with a fiberization
die fed by an external metering pump.
Actuation of the control valves 21 opens port 32 of each module 12
as described previously, causing polymer melt to flow through each
module 12. In the meltblowing segments 11, the melt flows through
manifold passage 75, through pump 15, into passages 76 and 77,
through side ports 38, through passages 37 and annular space 45,
and through port 32 into the die tip assembly 13. The pumps 15 used
in the present invention are similar in design to those of U.S.
Pat. No. 5,236,641. The polymer melt is distributed laterally in
the die tip 13 and discharges through orifices 53 as side-by-side
filaments 14. Air meanwhile flows from manifold passages 29, 103,
111, 109, 113, and 114 where the air is heated. Air enters each
module 12 through port 39 and flows through holes 49 and into slits
discharging as converging air sheets at or near the die tip apex of
the nose piece 52. The converging air sheets contact the filaments
14 discharging from the orifices 53 and by drag forces stretch them
and deposit them onto the underlying substrate in a random pattern.
This forms a generally uniform deposit of meltblown material on the
substrate.
Once production has begun, and the die assembly is in the
operational mode, the pattern of meltblown material may be varied
by switching any combination of the die segments from the
operational mode to the recirculation mode. Controller 3 of a
segment to be switched would command valve 21 of the fiberization
die module 12 to close while controller 4 would command valve 55 of
the recirculation module to open whereby the flow of polymer
through the discharge line from the pump switches from the die
module to the recirculation module. Because the die segments are
narrow in the machine direction, and because a large number of
segments may be employed, a wide variety of precisely placed
coatings may be produced. Die segments may be switched back and
forth between the operational mode and recirculation mode at the
will of the operator.
In each of the modules 12, the polymer and air flows are basically
the same, with the difference being, however, in the nozzle type
provided on the module. In the spiral nozzle, a monofilament is
extruded and air jets are directed to impart a swirl on the
monofilament. The swirling action draws down the monofilament and
deposits it as overlapping swirls on the substrate as described in
the above referenced U.S. Pat. No. 5,728,219. In the non-air
assisted nozzles, the air ports are sealed off, and only a
continuous bead or layer is dispensed from the die module. As noted
above the assembly 10 may be provided with different nozzles to
achieve a variety of deposition patterns.
Typical operational parameters are as follows:
Polymer Hotmelt adhesive Temperature of the 280.degree. F. to
325.degree. F. Die and Polymer Temperature of Air 280.degree. F. to
325.degree. F. I Polymer Flow Rate 0.1 to 10 grms/hole/min. Hot air
Flow Rate 0.1 to 2 SCFM/inch Deposition 0.05 to 500 g/m.sup.2
As indicated above, the die assembly 10 may be used in meltblowing
any polymeric material, but meltblowing adhesives is the preferred
polymer. The adhesives include EVA's (e.g. 20-40 wt % VA). These
polymers generally have lower viscosities than those used in
meltblown webs. Conventional hot melt adhesives useable include
those disclosed in U.S. Pat. Nos. 4,497,941, 4,325,853, and
4,315,842, the disclosure of which are incorporated herein by
reference. The preferred hot melt adhesives include SIS and SBS
block copolymer based adhesives. These adhesives contain block
copolymer, tackifier, and oil in various ratios. The above melt
adhesives are by way of illustration only; other melt adhesives may
also be used.
Although the present invention has been described with reference to
meltblowing hot melt adhesive, it is to be understood that the
invention may also be used to meltblow polymer in the manufacture
of webs. The dimensions of the die tip may have a small difference
in certain features as described in the above referenced U.S. Pat.
Nos. 5,145,689 and 5,618,566.
The typical meltblowing web forming resins include a wide range of
polyolefins such as propylene and ethylene homopolymers and
copolymers. Specific thermoplastics include ethylene acrylic
copolymers, nylon, polyamides, polyesters, polystyrene, poly(methyl
methacrylate), polytrifluoro-chloroethylene, polyurethanes,
polycarboneates, silicone sulfide, and poly(ethylene
terephthalate), pitch, and blends of the above. The preferred resin
is polypropylene. The above list is not intended to be limiting, as
new and improved meltblowing thermoplastic resins continue to be
developed.
The invention may also be used with advantage in coating substrates
or objects with thermoplastics.
The thermoplastic polymer, hot melt adhesives or those used in
meltblowing webs, may be delivered to the die by a variety of well
known means including extruders metering pumps and the like. It
will be understood by those skilled in the art that the present
invention may be used with air assisted or non-air assisted die
assemblies.
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